1. Field of the Invention
The present invention is directed to the manufacture of electrical and electronic devices having an integral thin-film type battery electric power source, by using semiconductor fabrication techniques, and more particularly, to the manufacture of electrical and electronic devices having self-contained vertically integrated and interconnected thin-film type batteries whereby the device area is minimized, enabling a higher degree of integration, and to the devices manufactured thereby.
2. Description of the Background Art
As the manufacture of electrical and electronic devices by employing semiconductor fabrication techniques has increasingly being more commonplace, the size of such devices has become miniaturized, and their power consumption requirements have accordingly also been reduced. In use, such devices are typically mounted on a substrate or carrier, and supplied with necessary electric power from an externally connected power source or supply.
Recently, thin-film type batteries usable as an electric power source for electrical and electronic devices have been developed. Such thin-film type batteries are attractive because they are stable in operation, are capable of high energy output and make it possible to minimize the size of a battery power source. Furthermore, because they can be manufactured using familiar thin-film fabrication techniques, such batteries can be usefully employed as power sources for miniaturized electrical and electronic devices.
An example of such a thin-film type battery is disclosed in U.S. Pat. No. 5,338,625, wherein it is suggested that a thin-film battery cell could be fabricated directly onto a semiconductor chip, the chip package or the chip carrier. A possible application thereof as proposed in U.S. Pat. No. 5,338,625 and as represented in FIG. 1 herein, is a thin-film rechargeable battery as a primary or standby power source for low current devices, which includes a Li-VO.sub.x thin-film battery cell 3 deposited onto a semiconductor chip package, with current leads 8 extending from the cell 3 to a semiconductor chip 2 mounted on the chip package. The thin-film battery cell as proposed therein would occupy an area of one square centimeter on the chip package, although it is further proposed therein that the capacity and current density of the battery could be increased by depositing a larger battery over the unused area of the chip package.
The use of thin-film batteries as power sources for miniature electrical and electronic devices is appealing, in that such batteries can be fabricated using similar techniques and processing as are employed for fabricating such devices. Also, such batteries can be freely fabricated in various shapes and sizes as desired. However, from the viewpoint of achieving higher integration of electrical and electronic devices, it is desirable to reduce the area occupied by such devices, and in case of integrating a thin-film battery as an "onboard" power source for such devices, it is thus desirable that the area occupied by the battery itself should be minimal. But the thin-film battery power source proposed in U.S. Pat. No. 5,338,625, being fabricated in horizontal or planar alignment with the semiconductor chip, that is, being laterally removed on the chip package from the chip, consequently occupies a significant area in addition to the area occupied by the chip itself, and such a horizontal arrangement of the battery and device does not admit of higher integration. Also, the lateral disposition of the thin-film battery relative the chip also necessitates current leads extending therebetween to be fabricated or otherwise provided on the chip package for enabling electrical interconnections therebetween, further increasing the area occupied by such an arrangement and complicating the fabrication process.
Moreover, although it is suggested in U.S. Pat. No. 5,338,625 that a thin-film battery could be fabricated directly onto a semiconductor chip, there is no disclosure therein as to how this could be accomplished, nor how the necessity could be avoided for externally providing current leads between the battery and the chip.
Thus, there has remained a need for integrating electrical and electronic devices with thin-film battery power sources in a way that minimizes the overall area occupied by such a combination and which lends itself to a higher degree of device integration in line with the trend of increasing miniaturization of micro-devices, and which uses current semiconductor and thin-film fabrication techniques.